All patents, patent applications, and publications cited within this application are incorporated herein by reference to the same extent as if each individual patent, patent application or publication was specifically and individually incorporated by reference.
The invention relates generally to the organic chromophores for second order nonlinear optical (NLO) applications, compositions including such chromophores, and applications including such chromophores and compositions.
The development and uses of NLO chromophores, including polymer matrix development, waveguide fabrication, and optical device fabrication are well documented. An NLO chromophore (also known as a xe2x80x9cpush-pullxe2x80x9d chromophore) comprises three fundamental building blocks represented by the general formula D-xcfx80-A, where D is a donor, xcfx80 is a xcfx80-bridge, and A is an acceptor. In the art, a xe2x80x9cxcfx80-bridgexe2x80x9d is sometimes referred to as a xe2x80x9cxcfx80-conjugated bridge,xe2x80x9d xe2x80x9cxcfx80-electron bridge,xe2x80x9d xe2x80x9cconjugated xcfx80-electron bridge,xe2x80x9d and the like. Examples of such bridges are described, for example, in U.S. Pat. Nos. 5,670,091, 5,679,763, 6,067,186, and 6,090,332. A xe2x80x9cxcfx80-bridgexe2x80x9d allows charge transfer from a donor to an acceptor in a chromophore. Exemplary acceptors are shown in FIG. 1, where, independently at each occurrence, R1 is hydrogen, a halogen except when bonded to a carbon alpha to or directly to a nitrogen, oxygen, or sulfur atom, or an alkyl, aryl, heteroalkyl, or heteroaryl group; Y is O, S or Se; and q is 0 or 1. Exemplary donors are shown in FIG. 2, where, independently at each occurrence, R1 is hydrogen, a halogen except when bonded to a carbon alpha to or directly to a nitrogen, oxygen, or sulfur atom, or an alkyl, aryl, heteroalkyl, or heteroaryl group; R2 is hydrogen or an alkyl, aryl, heteroalkyl, or heteroaryl group; Y is O, S or Se; m is 2, 3 or 4; p is 0, 1 or 2; and q is 0 or 1. Herein, a heteroalkyl group includes, but is not limited to, functional groups, halogen substituted alkyl groups, perhalogenated alkyl groups, and dendrons. What is meant by a functional group in generally understood in the art of organic chemistry, for example see Appendix B in Jerry March, xe2x80x9cAdvanced Organic Chemistryxe2x80x9d 4th Edition, John Wiley and Sons, New York, pp 1269-1300. A xe2x80x9cdendronxe2x80x9d is a substituent that has regularly repeating subunits. A dendron may be further comprised of one or more heteroaryl group. A xe2x80x9cdendrimerxe2x80x9d is a macromolecular structure that contains a xe2x80x9ccorexe2x80x9d surrounded by one or more dendrons. Often in the art, the terms dendron and dendrimer are used interchangeably. Dendrons and dendrimers are illustrated and discussed in Bosman et al., Chem. Rev. 1999, 99, 1665 and U.S. Pat. No. 5,041,516.
The particular D-xcfx80-A arrangement affects the ability of the molecule to achieve large second order NLO effects. Thus, the first molecular electronic hyperpolarizability (xcex2, sometimes given as xcexcxcex2, where xcexc is the dipole moment of the chromophore), which is a measure of this ability, can be tuned and optimized by changing the electronic properties of any one of D, xcfx80, or A, see Gorman and Marder Proc. Natl. Acad. Sci, USA 1993, 90, 11297. Molecular NLO effects, in turn, can be translated into bulk EO activity in a material by aligning molecules in one direction by applying an electric field.
In one aspect, a nonlinear optical chromophore has the formula D-xcfx80-A where xcfx80 is a xcfx80 bridge including a thiophene ring having oxygen atoms bonded directly to the 3 and 4 positions of the thiophene ring, D is a donor, and A is an acceptor. The oxygens bonded directly to the 3 and 4 ring positions of the of the thiophene ring may be further independently substituted with an alkyl group comprising 1 to about 20 carbons, a heteroalkyl group comprising 1 to about 20 carbons, an aryl group comprising 1 to about 20 carbons, or a heteroaryl group comprising 1 to about 20 carbons.
In a second aspect, a nonlinear optical chromophore has the formula: 
wherein, independently at each occurrence: xcfx801 is absent or a xcfx80-bridge; xcfx802 is absent or a xcfx80-bridge; D is an donor; A is an acceptor; X is O or S; and R is an alkyl group comprising 1 to about 20 carbons, a heteroalkyl group comprising 1 to about 20 carbons, an aryl group comprising 1 to about 20 carbons, or a heteroaryl group comprising 1 to about 20 carbons. These chromophores may be combined with a polymer matrix to form second order nonlinear optical compositions useful in a variety of applications, including electro-optic devices such as optical modulators, optical switches, and optical directional couplers. For example, the chromophore and polymer matrix may contain crosslinkable functional groups, and may be combined to form a guest-host composite, in which the chromophore is the guest and the polymer matrix is the host. An electric field is then applied to the composite to induce electro-optic activity, after or during which the composite is crosslinked to covalently bond the chromophore to the polymer matrix. Other features and advantages of the invention will be apparent from the following description of preferred embodiments thereof, and from the claims.